David unpacked 79 kilograms of peaches and melons. The peaches came in 5-kilogram bags and the melons came in 7-kilogram bags. In all, David unpacked 13 bags of fruit. How many bags of peaches and bags of melons did he unpack?

?=bags of peaches

?=bags of melons

you have to guess and check the word problems

please please please help me